Number 21

"Number Facts & Properties" Calculator

What is number 21?

Answer

Number 21 is

an odd number

Twenty-one

The last digit, 1, is odd, so 21 is odd: 21 = 2 × 10 + 1.

How to read it

Ordinal

twenty-first

Divisibility

no — composite

Prime factorization

21 = 3 × 7

4: 1, 3, 7, 21

Nearest primes

19 and 23

Other notations

XXI

10101

15

Digits

Number of digits

2

Sum of digits

2 + 1 = 3

Product of digits

2 × 1 = 2

Codes

QR code

Barcode (Code 128)

Related Calculations

See Also

Decimal to Binary Converter - Decimal numbers to Binary conversion
Numbers to Roman Numerals - Decimal numbers to Roman numerals conversion
Factors of a Number - List all Factors and Factor Pairs of a Number
Prime Number Checker - Find out whether a given number is Prime or not
Prime Factorization - Prime Factorization Calculator
Prime Numbers List - List of all Prime Numbers - how many Prime numbers are between

Neighboring Numbers

Number	Even/Odd
6	Even
7	Odd
8	Even
9	Odd
10	Even
11	Odd
12	Even
13	Odd
14	Even
15	Odd
16	Even
17	Odd
18	Even
19	Odd
20	Even
21	Odd
22	Even
23	Odd
24	Even
25	Odd
26	Even
27	Odd
28	Even
29	Odd
30	Even
31	Odd
32	Even
33	Odd
34	Even
35	Odd

FAQ

What is number 21?

Number 21 is an odd number

Is 21 even or odd?

21 is an odd number

How many digits does 21 have?

The number 21 has 2 digits